Resins produced from the reaction of epoxides and dimethylol-propionic acid

ABSTRACT

COATING SYSTEMS APPLICABLE BY CONVENTIONAL COATING TECHNIQUES AS WELL AS BY ELECTROPHORETIC COATING ARE PROVIDED BY REACTING A HYDROXYCARBOXYLIC ACID SUCH AS DIMETHYLOPROPIONIC ACID WITH AN EPOXY RESIN AND OPTIONALLY ANY OF A DIBASIC ACID AND A DIOL IN THE ABSENCE OF AN EXTERNALLY ADDED ESTERIFICATION CATALYST AND CURING THE THUS OBTAINED PRODUCT. A VARIETY OF COATING SYSTEMS IS OBTAINED INCLUDING WATER-SOLUBLE RESINS OBTAINED BY NEUTRALIZING WITH AN AMINE THE REACTION PRODUCT PRIOR TO CURING.

United States Pate'nt O 3,707,526 RESINS PRODUCED FROM THE REACTION OFEPOXIDES AND DIMETHYLOL-PROPIONIC ACID John Allister Gannon and ArthurAllen Tracton, Toms River, N.J., assignors to Ciba-Geigy Corporation,Ardsley, NJ. N Drawing. Continuation-impart of application Ser. No.789,948, Jan. 8, 1969. This application Nov. 16, 1970,

Ser. No. 90,014

Int. Cl. C08g 30/12 US. Cl. 260-47 EA 16 Claims ABSTRACT OF THEDISCLOSURE CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of application Ser. No. 789,948, filed Jan. 8,1969, and now abandoned.

BACKGROUND OF THE INVENTION In recent years there has been a markedtrend toward the use of various resin materials as coatings includingwater-based coating systems based on, among other considerations, theelimination of the use of volatile solvents with their attendant hazardsand recovery costs and on the fact that Water is an inexpensive solvent.

In view of the excellent properties characterizing epoxy based coatingcompositions, considerable effort has been expended in the search forsatisfactory epoxy coating systems using either Water or non-volatileorganic systems. None of the systems developed so far has beencompletely satisfactory and the achievement of an epoxy resin basedsystem providing optimum properties is the object of continuing researchettorts. The esterification reaction between certain hydroxy carboxylicacids and epoxy compounds is known in the art. In reacting suchcompounds together, two types of reactions may result owing to thechemical nature of the material used. Thus, the hydroxyl group of thehydroxy acid may react with the epoxide group to form ether linkages, orthe carboxyl group of the acid may react with the epoxide to form estergroups. Both reactions may occur in an uncontrolled reaction to yield aproduct having mixed ether and ester linkages to a non-predeterminedextent. Such circumstances with the epoxides and acids previouslyemployed have not been tolerable since the ultimate product has not beensuitable to any great extent for any practical purposes.

In an effort to overcome this, the art has attempted to optimize theesterification part of the reaction above referred to while minimizingthe ethen'fication part. This has been achieved by providing in thereaction medium an externally added esterification catalyst. Suchmaterials are normally basic and are represented by tertiary amines,quaternary ammonium salts and the like. This situation has beenespecially true of attempts at reacting certain hydroxy tertiarycarboxylic acids such as dimethylolpropionic acid (DMPA), for whileother hydroxy acids have been reacted with epoxides in the absence of anesterifiction catalyst, the art has always regarded an esterificationcatalyst as necessary when using DMPA in reaction with an epoxide.Typical of this approach is that taken in US. Pat. No. 3,404,018.

SUMMARY OF THE INVENTION In accordance with the present invention, ithas now been discovered that dimethylolpropionic acid can be reactedwith an epoxide resin in the absence of an externally addedesterification catalyst, and optionally in the presence or absence of adibasic acid or a diol, to produce curable resins having very desirablephysical properties. The physical properties are especially manifestedin film coatings obtained from the products of the invention aftercuring. Thus, the products can be directly cured as described below toyield coatings suitable for metal can liners, coil coatings, moldingresins, adhesives, laminating resins and the like. Alternatively, theproducts can be treated with an amine, when an excess of acid has beenused, to convert the resin to a water-soluble form with subsequentcuring. Coatings, films and castings obtained from the products of thepresent invention are characterized by good adhesion, flexibility, colorand resistance to impact, abrasion and attack by chemicals and alkalisolutions.

DESCRIPTION OF THE PREFERRED EMBODIMENT The epoxy compounds employed arethose epoxy compounds having a weight per epoxide of from to 530. Thus,the epoxy compound can be either liquid or solid and can be employedeither per se or in the form of blends.

As epoxide compounds there can be used esters such as are obtainable bythe reaction of a dior polybasic carboxylic acid with epichlorohydrin ordichlorohydrin in the presence of an alkali. Such esters may be derivedfrom aliphatic dicarboxylic acids, such as oxalic acid, succinic acid,glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,sebacic acid, and especially aromatic dicarboxylic acids, such asphthalic acid, terephthalic acid, 2:6-naphthalene-dicarboxylic acid,diphenyl-ortho:ortho'-dicarboxylic acid, ethylene glycolbis-(para-carboxyphenyl) ether or the like. Others which may be usedare, diglycidyl esters which correspond to the average formula:

in which X represents an aromatic hydrocarbon radical, such as a phenylgroup, and Z represents a small whole number or a small fractionalnumber.

There may also be employed the polyglycidyl ethers such as areobtainable by the interaction of a dihydric or polyhydric alcohol or adiphenol or polyphenol with epichlorohydrin or related substances, forexample, glycerol dichlorohydrin, under alkaline conditions oralternatively in the presence of an acidic catalyst with subsequentalkaline treatment. These compounds may be derived from glycols, such asethylene glycol, diethylene glycol, triethylene glycol propyleneglycol-1:2, propylene glycol- 1:3, butylene glycol-1:4,pentane-lzS-diol, hexane-1:6- diol, hexane-2:4:6-triol, glycerine andespecially diphenols or polyphenols such as pyrocatechol, hydroquinone,1:4-dioxynaphthalene, 1:5 dioxynaphth-alene, phenolformaldehydecondensation products, cresol-formaldehyde condensation products,bis-(4-hydroxy phenyl)-methane, bis (4-hydroxyphenyl)-methanephenylmethane, bis-(4- hydroxyphenyl)-tolylmethane, 4:4-dioxydiphenyl,bis-(4- hydroxyphenyl)sulphone and (for preference) 2:2-bis-(4-hydroxyphenyl) propane. There may also be employed diglycidyl etherswhich correspond to the average formula:

As regards the third and fourth components, when employed, these areconveniently used at molar ratios ranging from .1 to 2 and preferablyone mole per mole of DMPA used.

'acid terminated dimer of linoleic acid. Acid terminated polyesters andpolyethers may be employed as well.

In general, the diol component when used can be any dihydric alcoholincluding hydroxy terminated polyethers and polyesters. Preferred use ismade of the glycols such as tetrarnethyleneglycol, hexamethyleneglycoland pentamethyleneglycol. The optional use of these dibasic acids anddiols is governed by the desirability of introducing difierentstructural features into the final resin. This will be largely withinthe preferences of the individual fabricator.

The reaction between the epoxide and the dimethylolpropionic acid iscarried out at elevated temperatures preferably at from about 135 C. toabout 180 C. with a temperature of between 145 C. to 155 C. beingpreferred. While it is possible to work at temperatures above 180 C.,the possibility of self-esterification occurring at such temperaturesrenders it generally undesirable to employ such temperatures. Similarly,while temperatures below 135 C. could be employed, thedimethylolpropionic acid is not sufiiciently molten at such lowertemperatures for satisfactory reaction. The reaction is normallycomplete in about 8 to 10 hours although shorter or longer times in therange of 5 to hrs. produces suitable results.

The relative proportions of reactants utilized in carrying out theprocess of the invention, to a large extent, is dictated by the resultsdesired in the final cured product. In general, the molar ratios ofepoxide to dimethylolpropionic acid range from 1:3 to 1:0.3 arepreferably 0.9:1 to 1.1:1 are employed. For such purposes a mole ofepoxide is considered as containing 2 epoxy groups. For producing resinssuitable for use as molding resins curable with conventional epoxycuring agents such as anhydrides and the like, a molar excess of theepoxide of the order of 23:1 is suitable. Epoxide:DMPA mole ratios of122-3, i.e. excess acid are normally employed where it is desired toproduce water-soluble curable resins by neutralization as discussedbelow. Preferred, when can liner resins are ultimately desired, are moleFittlQS 01? from 0.9-1.1 most preferably unity,

The above recited reactions may be carried out with or without solvent,but it is generally suitable to use no solvent. Under somecircumstances, as when unconsumed epoxy groups are present, it ispreferred to use a nonvolatile polar solvent as a reaction vehicle.Suitable solvents are Cellosolve acetate, cyclohexanone, high boilingethers and the like. The reaction can be run at solids levels of 50 toand preferably 65 to 85% by weight of reaction product in the solventsystem. Indeed these levels of final product in the solvent representsuitable materials for commercial use and sale.

The products of the invention are characterized by being curable inrelatively short cure times when cured with conventional epoxy curingsystems. Of particular suitability as curing agents are those containinga reactive hydrogen atom such as urea-formaldehyde, phenolformaldehydeor melamine-formaldehyde condensation products. As stated above, theresins of the invention, when excess acid is employed, can beneutralized to render them water soluble. Neutralization of the reactionproduct is effected by an amine. In general, any amine, primary,secondary or tertiary, and aliphatic, aromatic or heterocyclic, as wellas ammonia can be employed. Preferred use is made of the alkanolamines,such as dimethylaminoethanol. Illustrative of the compounds which can beemployed are ammonia, ethanolamine, triethanolamine, morpholine,diethylamine, 2-amino-2-methyl-lpropanol,2-amino-2-methyl-1,3-propanediol and tris(hydroxymethyl)-aminomethane.

The products of the invention, that is the reaction product of DMPA withthe epoxide and optional ingredients, produced as they are in theabsence of any externally added esterification catalyst, differ fromcompounds of the art produced with a catalyst. That is, the instantcompounds, rather than being almost completely made up of esterlinkages, actually contain from 80 to 40 percent of ester -groups andfrom 20 to 60 percent ether groupings. This relatively high percentageof ether linkages renders the product substantially different from thoseof the art and no doubt contributes to the desirable physical propertiesthat the resins display upon subsequent curing.

The following examples serve to illustrate the invention.

'Example 1 112 grams of azelaic acid and 160 grams of dimethylolpropionic acid are charged to a reaction vessel. The mixture is heatedslowly to 150 C. under a nitrogen atmosphere. 370 grams of Araldite6005, a liquid epoxy resin having an epoxy value of 0.54 eq./ g., aspecific gravity of 1.17 at 25 C. and a viscosity of 1215,000 cps. at 25C. on the Brookfield viscometer, prepared by reacting 4',4-dihydroxydiphenyl propane and epichlorohydrin in a molar ratio of l to about 10are added to the reaction mixture over a period of 1 hour. The mixtureis held at C. for an additional period of 1 hour. The reaction mixtureis then diluted with 150 parts of methyl Cellosolve. The reactionmixture is cooled to 95 C. and 76 grams of dimethyl amino ethanol areadded slowly. The reaction temperature is controlled at from 95-100 C.and the reaction mixture stirred at 8595 C. for a period of 30 minutesat the end of which period 150 parts of water are added. The reactionmixture is stirred for an additional 30 minutes at 85-95 C. and is thenfiltered under pressure at 85-95 C. to provide a product having aviscosity of 45,000-55,000 cps., a solids content of 60%, a flash-pointof 175 F. and a color of maximum and being dilutible with water.

The above procedure is repeated employing equivalent amounts of adipicacid, diglycoiic acid, dimerized fatty acid (Empol 1016), 1,4-butanedioland 1,5-pentanediol, respectively, in place of the azelaic acid employedabove and employing isopropanol in place of the methyl Cellosolveemployed above.

Products having similar properties are obtained.

The above procedure is again repeated, employing 86 grams oftriethylamine in place of the 76 grams of dimethylaminoethanol employedabove. A product of similar properties is obtained.

Example 2 370 grams of Araldite 6005, 22 grams of 1,4-butanediol and 47grams of azelaic acid are charged to a reaction vessel. The mixture isheated to 150 C. under a nitrogen atmosphere with stirring and held at150 C. for about 1 hour. 160 grams of dimethylol propionic acid are thencharged to the reaction mixture which is held at 150 C. until an epoxycontent of less than 0.1 eq./kg. is achieved. The batch is then dilutedwith 138 grams of methyl Cellosolve. The temperature of the reactionmixture is lowered to 95 C. and the reaction mixture neutralized by theaddition of 76 grams dimethylaminoethano]. The neutralized reactionmixture is agitated at 85- 95 C. for 30 minutes. 138 grams of water areadded and the mixture stirred for a further period of 30 minutes at85-95 C. followed by filtration under pressure. A product having similarproperties to those of Example 1 is obtained.

Example 3 The product of Example 1 is employed as a vehicle in anunpigmented system by admixing therewith as crosslinking agent 25 partsper hundred parts of resin of a melamine-formaldehyde condensationproduct, obtained by reacting 2.4 mols of formaldehyde with 0.3 mol ofmelamine in an aqueous medium at pH of 7.5 and at a temperature of 1000, followed by filtration, washing with water and drying at 120-130 C.

The above composition comprising the resin and crosslinking agent isspread with a doctor blade on clean steel panels. The coated panels arethen heated at 149 C. for 30 minutes. The film obtained was 0.7 milthick, had good adhesion and flexibility, a reverse impact strength of28 inch-pounds and satisfactory resistance to water, xylene and 5%caustic soda solution.

Example 4 The product of Example 2 is employed as a vehicle in anunpigmented system by admixing therewith in two separate vessels 11 and25 parts per hundred parts of resin respectively of amelamine-formaldehyde condensation product obtained according to theprocedure described in Example 3.

The compositions are spread with a doctor blade on clean steel panels.The coated panels are then heated for 30 minutes at 177 C. with theresults shown in the table below.

6 EXAMPLE 5 A representative composition for electrophoretic coatmgapplication is prepared by mixing the following components:

G. Product of Example 1 133.3 Cymel 300 (a melamine-formaldehydecondensation product) 20.0 Red iron oxide 25.0 Anionic emulsifier* (20%solids) 10.0 Butyl Cellosolve 100.0 Water 981.7

*Triton X301 :1 sodium alkyl aryl polyether sulfate.

The above composition is applied by electrodeposition to clean steelpanels which have been phosphate primed.

The panels are plated employing a schedule comprising 10 VDC forseconds, followed by washing with demineralized water, blowing airacross the surface of the panel and then curing for 30 minutes at 177 C.

The coated panels were characterized by good adhesion, flexibility, andimpact strength and satisfactory resistance to water and xylene.

While use has been made above of melamine-formaldehyde condensationproducts as the water-soluble hardeners, it is to be recognized thatamino-aldehyde condensation products generally can be employed.

Example 6 A three-neck, round-bottom flask equipped with refluxcondenser, stirrer, thermometer and heating mantle is charged with 1mole (380 g.) of CIBA Araldite 6010, a liquid epoxy resin made fromBisphenol A and epichlorhydrin having an epoxy value of 0.51-0.55 eq./100 grams, a specific gravity at 25 C. of 1.164 and a viscosity of12,000-16,000 cps. at 25 C. on the Brookfield viscometer, 1 mole (134g.) of dimethylolpropionic acid and a quantity g.) of Cellosolve acetatesolvent sufficient to provide an 80% solids solution. The reactionmixture is heated at 150 C. for 9 hours at which time analysis shows anacid number of 3.5 and an epoxy content of 0.33 eq./kg. The reactionmixture is diluted to 50% with methyl Cellosolve and xylene so as tomaintain a 1:1:1 by weight overall solvent mixture including theCellosolve acetate initially charged. The reaction product containsapproximately 50% of ether groups and 50% of ester groups.

The resin solution is next blended with a 60% solids solution of aurea-formaldehyde resin (Reichhold P-196- 60) in the proportion of 80parts of the former to 20 parts of the latter, and the resultant coatingsolution is employed to prepare coatings on aluminum panels. Thesecoatings are resistant to solvents and acid after oven bakings threeminutes at 350 F.

Example 7 A three-neck, round-bottom flask equipped with a refluxcondenser, stirrer, thermometer and heating mantle is charged with 2.2moles (595 g.) of 3,4-epoxy cyclohexylmethyl-3',4'-epoxy cyclohexanecarboxylate (CY 179) having the following properties:

Viscosity 350 cps. at 25 C. Weight per epoxide of gms.

and heated to C. One mole (134 g.) of dimethylolpropionic acid is thenadded to the CY-179 in equal increments over a period of 1 hour.

The reaction mixture is then held at 150 C. for an additional hour,whereupon analysis shows an acid num- Reverse Hardener impact,Resistance concentration Adhesion Flexibility in.-1b. water Xylene 5%NaOH 11.1 phr Excellent Good 128 Satisfactory-.. Satisfactory---Satisfactory. 25.0 nhr Fair Fair 4 do do Do.

ber equal to zero. The reaction mixture is discharged as 100% solids toprovide a solid resin upon cooling and possessing a Durrans softeningpoint of 86 C. and an epoxy content of 2.48 eq./kg. The reaction productcontains about 50% ether and about 50% ester groups.

Example 8 CHI We claim:

1. A process which comprises reacting at elevated temperaturesdimethylolpropionic acid and a 1,2-epoxy compound having a weight perepoxide of from about 180 to about 530 in a molar ratio of epoxide todimethylolpropionic acid of 1:3 to 1:03 and in the presence of a dibasicacid selected from the group consisting of aliphatic dicarboxylic acidand dimerized fatty acid, or mixtures thereof in the absence of anexternally added esterification catalyst; and when unconsumed epoxide ispresent, using a non-volatile polar solvent as a reaction vehicle.

2. A process according to claim 1 wherein the reaction is carried out atfrom about 135 C. to about 180 C.

3. A process according to claim 2 wherein the epoxy compound is a liquidat room temperature.

4. A process according to claim 3 wherein the epoxy compound has theaverage formula The reaction mixture is then heated at 150 C. for an 25in which Z represents a small whole number or fractional additionalhour, whereupon analysis shows an acid number equal to 13, together withan epoxy content of 0.43 eq./kg. The product has 60% ether groups and40% ester groups. The resin is then diluted to 60% solids content withmethyl Cellosolve to provide a coating vehicle. Admixture of the vehiclewith a urea-formaldehyde resin in the proportion of 80 parts to parts ofthe latter provides a coating solution which is used to prepare coatingson aluminum panels. These coatings are resistant to solvents such asxylene, methyl isobutyl ketone and acetone after baking for 3 minutes at350 F.

CH?- (1H Example 9 A three-neck, round-bottom flask equipped with refluxcondenser, stirrer, thermometer and heating mantle is charged with 2moles (760 g.) of CIBA Araldite 6010, 0.5 mole (282 g.) of Empol 1014dimer acid, which is essentially dimerized linoleic acid and 0.5 mole(67 g.) of dimethylolpropionic acid.

The mixture is then heated to 170 C. with agitation and held at thattemperature until an acid number of 1.0 is reached (approximately 5hours). The reaction mixture is then diluted to 60% solids with a 1:1mixture by weight of Cellosolve acetate/xylene. Blending of the resinsolution with a urea-formaldehyde resin in the ratio of 80 parts to 20parts by weight yields cured films after baking 3 minutes at 350 F.

Example 10 A four-neck, round-bottom flask equipped with mechanicalagitation, reflux condenser, thermometer and dropping funnel is chargedwith 2 moles (268 g.) of dimethylolpropionic acid and heated to 150-155C. under nitrogen. 1 mole (380 g.) of CIBA Araldite 6005 is slowly addedvia a dropping funnel to the molten acid over a period of 1 hourmaintaining the reaction temperature. At the conclusion of the feed thereaction mixture is held for an additional 30 minutes whereupon theepoxide content is 0 and the acid number is equal to 100. The reactiontemperature is then lowered to around 130 C. and the product is dilutedwith butyl Cellosolve to 60% nonvolatiles and pressure filtered. Thebatch is cooled to 35 C. and 100% neutralized with dimethylaminoethanolbased on the acid number obtained.

number.

5. A process according to claim 1 wherein the dibasic acid is analiphatic dicarboxylic acid.

6. A process according to claim 5 wherein the aliphatic dicarboxylicacid is azelaic acid.

7. A product obtained by the process of claim 5 characterized in that itcontains from -40% ester groups and from 20-60% ether groups.

8. A product according to claim 7 wherein the epoxy compound is liquidat room temperature.

9. A product according to claim 7 wherein the epoxy compound has theaverage formula in which Z represents a small whole number or fractionalnumber.

10. A process which comprises neutralizing with an amine the productobtained by the process of claim 1.

11. A process according to claim 10 in which the amine is analkanolamine.

12. A process according to claim 11 in which the alkanolamine isdimethyl aminoethanol.

13. The product obtained by neutralizing with an amine the productobtained by the process of claim 1.

14. A product according to claim 13 in which the amine is analkanolamine.

15. A product according to claim 14 in which the alkanolamine isdimethylarninoethanol.

16. A process of claim 1 wherein the ratio of epoxide todimethylolpropionic acid is 0.911 to 1.1:1.

References Cited UNITED STATES PATENTS 3,404,018 10/1968 Hicks 26075 EP3,464,939 10/1969 Westrenen 26018 EP WILLIAM H. SHORT, Primary ExaminerT. PERTILLA, Assistant Examiner US. Cl. X.R.

117-127, 128.4; 161-186, 161ZB;2602 EP, 2 EA, 18 EP, 29.2 EP, 31.4 EP,32.8 EP, 33.2 EP, 33.6 EP, 37 EP, 47 EP, 59, 78.3 R, 78.4 EP, 823, 831,834, 835, 860

